Bacterial vaginosis (BV) is the most prevalent cause of symptomatic vaginal discharge in women. Its etiology is unknown, however it is characterized by displacement of the normal vaginal flora with large numbers of anaerobic and facultatively anaerobic bacteria Epidemiologic associations exist between BV and sexually transmitted diseases (STDs) of the lower and upper female genital tract, however cause and effect are not known. The specific aims of this proposal are to determine the impact of BV on the acquisition of sexually transmitted female genital tract infections and to clarify the pathogenesis of BV. The role of Mycoplasma genitalium as well as newly described biotypes of Ureaplasma urealyticum in BV will be explored. A large cohort of women at high-risk for BV and STDs will be followed prospectively for 6 months. Extensive behavioral and clinical data collected during these visits as well as home diaries and self-obtained home vaginal smears will be used to create a time-line of events. Additionally, independently obtained behavioral data from the male partners will be available from Project #1 (Etiology of Nongonococcal Urethritis) in this STD CRC proposal. If the hypothesis advanced is correct, i.e. the presence of BV facilitates acquisition of STDs and if the pathogenesis of BV can be further clarified, then primary prevention of BV could substantially impact STD control. This project will interact significantly with Projects 1 and 4 of this proposal with overlap of study populations, behavioral data, and clinical specimens.